Broad band sources and systems are well known in the art and are for example described in EP2081 074, WO15003714 and WO15003715.
WO15003714 discloses a supercontinuum light source comprising a microstructured optical fiber and a pump light source, where the microstructured optical fiber comprises an intermediate tapered section. Thereby a very broad and stable supercontinuum of light is obtained.
U.S. Pat. No. 8,731,009 discloses a super continuum light source comprising a pump source and a generator fiber for generating the supercontinuum, where the refractive index profile of the core of the generator fiber is arranged to allow modal cleaning of the light as it propagates to provide an optical super continuum with relatively high spectral density and/or good beam quality.
In general most of the prior art broad band sources are focused on generating supercontinuum light of high quality and/or which is spanning over increasingly broader band width, e.g. supercontinuum which is spanning further into the blue wavelength e.g. below 450 nm or even lower.
The generated light or fractions thereof are often used in high precision illumination procedures and/or high precision measuring procedures such as for stimulated emission depletion, for fluorescence imaging procedures for Optical Coherence Tomography (OCT) and/or for industrial inspection, such as metrology.
Usually the light or fractions of light generated by the broad band source is transmitted via a delivery fiber to an apparatus, such as an illumination apparatus and/or a measuring apparatus for use in the measuring process of the apparatus. Generally it is desired that the delivery fiber is simple to connect to the apparatus and it is well known in the art to use standard connectors such as connectors according to the standards IEC 61754-20, IEC 61754-15 or IEC 61754-13.
The prior art delivery fibers have usually been step index fibers having a relatively very narrow transmission band with because such fibers are easy to handle, easy to connectorize and have low transmission loss. In order to be capable of transmitting a broader band width is has been suggested to use of photonic crystal fiber (PCF) with air holes in their cross-sections as delivery fiber has been introduced; thereby the delivery fiber is capable of transmitting a broader band width. However, such holey PCF generally is difficult to connect and may result in undesired power loss.